Area Forecast Discussion
Issued by NWS Los Angeles, CA

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000
FXUS66 KLOX 201852
AFDLOX

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
1152 AM PDT Thu Jul 20 2017

.SYNOPSIS...

An upper level ridge of high pressure will persist over the area
through the weekend. There will be areas of night through morning
low clouds and fog in most coastal and some valley areas. Temperatures
will be near or slightly above normal today, then rise a bit
through Saturday. Some cooling is expected Sunday into early next
week. Monsoonal moisture may bring some showers and thunderstorms
to the mountains and Antelope Valley Monday through Wednesday.

&&

.SHORT TERM...(TDY-SAT)

Overall, a quiet morning across the forecast district. Morning
sounding data indicates marine inversion between 1300 and 1500
feet deep this morning. Satellite/surface observations show
widespread stratus across Central Coast and more patchy stratus
south of Point Conception. Expect stratus to dissipate by late
morning for the coastal areas, with sunny skies for most areas
this afternoon. The only exception may be the San Gabriel
Mountains where some lingering mid-level moisture could generate
some afternoon cumulus buildups. Afternoon temperatures will hover
around seasonal normals today.

For the rest of the forecast, 12Z model data does not indicate any
major changes for the short term. At upper levels, ridge will
strengthen over the area through Saturday. This will help to make
the marine inversion more shallow with less inland penetration
indicated each morning. Additionally, the ridge will allow for a
warming trend Friday and Saturday. As for winds, models do
indicate some weak northerly gradients tonight and again Friday
night. So, there will likely be some gusty north winds across the
Santa Ynez range, but nothing approaching advisory levels at this
time.

.LONG TERM...(SUN-WED)

A weak upper low moving through the eastern Pacific will be
located off the coast of northern CA Sunday. The marine layer may
deepen a bit Sat night, but do not expect too much change in
night thru morning low cloud coverage Sat night/Sun morning, with
clouds confined mainly to the coast. However, there should be a
bit of cooling Sunday, mainly west of the mountains.

The upper low will move into northern CA and weaken on Monday,
then a broad trough will linger to the north of the region through
Wed. Heights and thicknesses across the region will fall Mon. The
marine layer will deepen, with night through morning low clouds
likely pushing into at least the lower valley location. Max temps
will likely be down a few degrees on Mon, down to slightly below
normal levels in most areas. The 00Z run of the GFS showed
increasing monsoonal moisture across the region Mon, enough for at
least a slight chance of afternoon and evening showers and
thunderstorms in the L.A. and VTU County mountains and the
Antelope Valley. Then, it showed monsoonal moisture extending
farther to the northwest Tue and Wed, with a slight chance of
tstms extending into the mtns of SBA County, the Cuyama Valley
and sern SLO County by Wed. The 06Z run of the GFS has trended
drier, especially for Wed, so those pops may have to be adjusted
by later shifts.

&&

.AVIATION...20/1800Z.

At 18Z, the marine layer depth was around 1700 ft deep at KLAX.
The top of the marine inversion was around 2200 ft with a
temperature of 20 degrees Celsius.

LIFR to IFR conditions will spread into primarily coastal
terminals after 03Z and through 10Z. Conditions should improve
one category between 14Z and 16Z with VFR conditions redeveloping
similar to today.

KLAX...IFR conditions will spread into KLAX between 08Z and
through 12Z. Conditions should improve one category between 14Z
and 16Z with VFR conditions redeveloping around 17Z.

KBUR...VFR conditions are expected throughout the period. There is
a 10 percent chance of MVFR conditions between 10Z and 16Z.

&&

.MARINE...20/900 AM.

High confidence that Small Craft Advisory winds will continue
through at least Saturday and possibly through Sunday across the
Outer Waters. There is a 20 percent chance of gale force winds
each afternoon and evening through Friday evening, mainly northwest
of the Channel Islands.

For the Inner Waters south of Point Conception, winds and seas
are expected to generally remain below advisory level through the
weekend.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...Beach Hazards Statement in effect from Friday afternoon
      through Sunday evening for zones 40-41-87. (See LAXCFWLOX).
PZ...Small Craft Advisory in effect until 9 PM PDT Saturday for
      zones 670-676. (See LAXMWWLOX).
     Small Craft Advisory in effect until 3 AM PDT Sunday for zone
      673. (See LAXMWWLOX).

&&

.HAZARD POTENTIAL OUTLOOK...(SAT-WED)
No significant hazards are expected during this period.

&&

$$

PUBLIC...Thompson/DB
AVIATION...Hall
MARINE...Hall
SYNOPSIS...DB

weather.gov/losangeles


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